Ontario's weather has become less predictable in recent years, with periods of intense rainfall followed by heat and humidity. For pest populations, this is essentially ideal breeding weather. Several of the most common household invaders in the GTA thrive in exactly these conditions — and a wet spring or summer almost always corresponds to increased call volume for pest control services.
Millipedes and sowbugs are among the most visible beneficiaries of high moisture conditions. Both species require humid environments to survive and will migrate indoors in large numbers when outdoor conditions become either too wet or too dry. They're harmless but alarming in large numbers, and their presence usually points to excess moisture around the foundation — mulch piled against siding, poor drainage, or gaps at the base of doors.
Earwigs follow a similar pattern. They breed in moist soil and organic debris, and a wet season dramatically increases the size of the population before the fall migration into homes. Cluster flies, which overwinter in wall voids and attics, are attracted to south-facing walls and accumulate in large numbers when conditions are right.
Perhaps more concerning is the connection between humidity and fungal growth inside homes. Moisture-damaged insulation and wood attract a range of secondary pests — fungus gnats, booklice, and certain beetle species — that would not otherwise be present. These pests are symptoms of a moisture problem rather than the cause, and addressing them requires both pest treatment and the underlying structural issue.
After a wet season, it's worth doing a baseline inspection of your basement, crawl space, and foundation perimeter. Addressing moisture points in the fall — before pests start seeking winter shelter — is one of the most cost-effective pest prevention steps a homeowner can take.
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